Distribution of electric potential and ion transport in the hypocotyl of Vigna sesquipedalis II. Axial potential difference

概要

論文の詳細を見る
Vital staining with pH indicator dyes made it possible to identify the xylem with the specific channel A, reported previously, through which hydrogen ions flow generating a resting potential difference along the germ axis as their diffusion potential. The distribution of K^+ concentration within this channel showed no similarity to electric potential distribution, in contrast to the distribution of H^+. The axial P.D. between both ends of a segment cut from a hypocotyl responded reversibly to the change in O_2 tension of the surrounding gas phase. After air had been quickly replaced by N_2, a lag period appeared before the sudden potential drop took place. The lag period (γ) was largely dependent on temperature. Apparent activation energy of the process characterized by 1/γ was 18Kcal/mole between 14-30℃, approximately equal to that of the O_2-uptake within the same temperature range. The relation between O_2 concentration and the maximum rate of recovery of P.D. from anoxia was of the Michaelis-Menten type; the apparent K_m was calculated as 2.1 × 10^<-5> M O_2, being of the same order as that of cytochrome oxidase in higher plants. The O_2-uptake rate "per unit of hypocotyl length" showed a distinct maximum in the elongating region where the axial distribution of both electric potential and pH within channel A had their minimums.
日本植物生理学会の論文